In known thread feeders of this kind (DE Patents No. 35 01 944 and 35 16 891 and U.S. Pat. No. 4,180,215) the feed drums have an entirely plain, continuous supporting surface and therefore entirely plain, continuous thread lead-in, storage or reserve and lead-out sections. Such thread feeders are used in continuously driven feed drums either for the positive and nonslip delivery of thread or for the non-positive friction feeding which is performed with slippage, and they operate satisfactorily with a great number of types of thread. In the use of other types of yarns, e.g. nontextured yarns such as polyester threads, however, filaments are frequently pulled out of the thread sections leaving the feed drum or even out of some of the coils of thread that are in the storage section. Aside from that, the high surface cling sometimes results in difficulties, at least in the case of some of the desired functions.
Attempts to carry the thread coils on the drum surface with reduced tension, or to provide that surface in a known manner (DE Pat. No. 33 26 099) with grooves, slots or ribs have led to no useful results.
On the other hand, to avoid this disadvantage, it has proven surprisingly to be especially advantageous to use thread feeders of another known kind (DE-OS 32 26 373, and DE Patent No. 35 06 490 and U.S. Pat. No. 4,669,677 ) which have rods in the storage section on which the threads are supported. Such thread-feeders have heretofore served mainly for applications in which the feed drums are driven intermittently in start-stop operation, since the thread supporting rods result in a reduction of the mass of the feed drums, and this is desirable for a rapid response when they are accelerated or stopped. Such thread feeders are not universally usable because the threads often call for friction conditions which can be assured only by feed drums having plain, continuous circumferential surfaces.
Therefore, in practice, there is a desire for thread feeding devices having feeder drums which can be provided with either plain, continuous surfaces or with rod-like support elements according to the thread material Such feeding devices have heretofore been unknown in connection with knitting machines. It would be conceivable to provide devices made in the form of spools which can be removably set on the feed cylinders and have plain, continuous surfaces of different coefficients of friction and/or diameters, in order thereby to provide for the different properties of the threads (U.S. Pat. No. 3,528,622). A similar application of this principle to feeding devices whose feed drums are provided selectively with plain, continuous circumferential surfaces or surfaces formed by rodlike supporting elements, it is not easily possible, for geometrical reasons.
It is an object of this invention to design the thread feeding apparatus of the kind described above such that, with little constructional difficulty, and expense, it will be able to operate either with the conventional plain, continuous storage section or with one formed of rod-like supporting elements, or optionally with reserve sections which are formed of rod-like supporting elements with different properties and/or systems selected according to the thread material. A further object is to design the thread feeding apparatus such that the changeover from one type of drum to the other is possible with little manipulation and with constructionally simple means.
For the solution of this object and according to this invention the thread feeding device is characterized in that the thread feeding element is a rod cage (23) consisting of a premanufactured component which has a lead-in element which contains the lead-in section and can be fastened for easy removal on the rotor (3,5), and which can be radially centered on the latter, and has a plurality of rod-like supporting elements (26) with support surfaces, said elements forming the storage section and being disposed substantially parallel to the axis of rotation such that the support surfaces are distributed on a cylindrical surface coaxial with the axis of rotation (4) or on a conical surface slightly tapered toward the end section (21), and said elements (26) having first ends fixedly joined to the lead-in element (24) and second ends which either are fastened to a mounting (25,41,47, 51) which can be joined to the rotor (3,5) and belong to the component, or are held directly on the rotor (3,5) and thereby radially centered with respect to the axis of rotation.
The invention offers important advantages in addition to the possible use of prefabricated cages. The removal of a cage for the purpose of cleaning, repair or replacement can be performed simply by pulling away its lead in element and, in some cases, the mounting. Likewise simple is the placement of a cage on the rotor. If simple clip-on or snap-on mechanisms are used, then not even a tool is necessary for the purpose. Only a few and very easily manufactured components are needed for the production of the cage. The down time of the knitting machine in the case of cleaning, repair or replacement operations, is limited virtually to the short amount of time needed for installation and removal. Retrofitting already existing thread feeders having conventional feed drums with the cages according to the invention is easily possible by providing the latter with appropriate lead-ins and mountings. If the lead-in is placed, for example, on an end section of the feed drum, the section of its surface that is important for the lead-in of the thread can be disposed in the axial direction substantially at the point where the thread enters the feeder even if a cage is not in place so that, when the cage is used, no readjustment of the thread lead-in or thread lead-out guiding means is necessary. Furthermore, the cages, like the feed drums already present, can be used to feed threads with or without slippage, in which case the fiber tearing or fiber separation that occur in the use of the former feed drums in connection with polyester threads or the like are no longer observed. Lastly, it is advantageous that the thread entry can take place along a substantially continuous surface, while the thread is guided within the storage area only on the rod like supporting elements.
Additional advantageous features of the invention will be seen in the subordinate claims.